Bone plate locking cannula and drill guide assembly

ABSTRACT

A bone plate locking cannula and drill guide assembly having a locking cannula detachably mountable onto screw-receiving apertures of a bone plate and a drill guide received within the locking cannula such that pilot holes are drilled through the apertures into bone at the proper angle to receive bone screws. The screw receiving apertures have a proximal bore of greater diameter than a distal bore, and the proximal bore is provided with internal threading to mate with external threading located on the distal end of the locking cannula. The bone screws are inserted through the locking cannula after removal of the drill guide and fastened into the bone to secure the bone plate in position without having to remove the locking cannulas from the bone plate, the internal diameter of the locking cannula bore being greater than the maximum diameter of the screw heads. The locking cannula is detached from the bone plate after the bone plate has been secured in place on the bone.

This application is a divisional application of U.S. patent applicationSer. No. 14/880,337, filed Oct. 12, 2015, now allowed, claiming thebenefit of U.S. Provisional Patent Application Ser. No. 62/115,990,filed Feb. 13, 2015.

BACKGROUND OF THE INVENTION

This invention relates in general to rigid metal plates adapted forattachment to bones (typically referred to as bone plates) withscrew-type fasteners (typically referred to as bone screws) and to guidedevices used to properly align a drill to create the bore in the bonethat will receive the screw-type fastener inserted through an aperturein the bone plate. The invention also relates to tubular drill guidesthat are used to properly align a drill bit when a pilot hole is beingdrilled into the bone.

With many bone fractures or surgical osteotomies it is necessary tosecure the bone segments in a fixed, rigid manner such that naturalhealing may occur. A common way to accomplish this is to provide a rigidmetal plate shaped and sized as required to correspond to the bone orbones being secured, the rigid plate having apertures to receive bonescrews, the bone screws being inserted through the plate and into thebone to secure the plate to bone and thereby prevent relative movementof the bone segments during the healing process. Additionally, boneplates are utilized in distraction procedures—the bone plates beingaffixed to opposing bone segments that are slowly separated by adistraction mechanism in known manner to lengthen the bone byosteogenesis. In most cases it is desirable or even necessary to firstdrill a pilot hole or bore into the bone at the location for each screwso as to prevent fracturing or splintering of the bone when the bonescrew is inserted. Given the need to reduce undesirable stresses withinthe bone material and to accurately and securely attach the bone plateto the bone, it is important that the bores are properly alignedrelative to the bone plate and screw receiving apertures, especiallywhen the screw receiving apertures are beveled, shouldered, threaded orotherwise configured to better mate or correspond to a particular bonescrew configuration.

While the pilot holes may be drilled by first marking the location ofthe screw receiving apertures on the bone through the screw-receivingapertures, removing the bone plate and then manually aligning the drillbit with the markings, a better known methodology for creating thescrew-receiving pilot holes is to utilize elongated, tubular drillguides that are aligned with the screw receiving apertures. The drillguides may be temporarily attached or mounted to the bone plates toextend proximally from the screw receiving apertures in order to insureproper location and alignment of the pilot hole and bone screw relativeto the bone plate. With such an assembly, the bone plate is manuallyheld or temporarily affixed in proper position over the bone or bonesegments, the drill bit is inserted into the drill guide so as to extendthrough the screw receiving aperture to the bone, the pilot hole iscreated in the bone, the bit is removed from the drill guide, the drillguide is detached from the bone plate, and the bone screw is insertedthrough the screw receiving aperture and into the pilot hole to securethe bone plate to the bone.

A problem that has been noted with the known systems is that the removalof the drill guide members from the bone plate prior to insertion of thebone screws into the apertures often results in movement of the boneplate relative to the bone or bone segments and the pilot holes thathave been created. This may result in misalignment of the bone screwswhen they are implanted to secure the bone plate to the bone ormisplacement of the bone plate.

It is an object of this invention to address this problem by providing abone plate locking cannula and drill guide assembly, and its method ofuse, wherein locking cannulas are temporarily attached to the bone platein proper alignment with the screw-receiving screw receiving apertures,the cannulas being sized to receive a tubular drill guide. The boneplate, screw receiving apertures, bone screws, drill bits, drill guidesand locking cannulas of the assembly are sized and structured such thatafter drilling the pilot bore into the bone and removing the drill bitand drill guide from the locking cannula, the internal diameter of thelocking cannula is sufficiently large such that the bone screw may beinserted through the cannula and driven into the bone through the screwreceiving aperture to secure the bone plate to the bone withoutrequiring removal of the locking cannula. After the bones screw is fullyinserted into the bone, the locking cannula is then removed from thebone plate. These and other objects not expressly set forth in thissection will be supported or made obvious based on the followingdisclosure.

SUMMARY OF THE INVENTION

The invention in various embodiments in general a bone plate lockingcannula and drill guide assembly comprising a bone plate and at leastone locking cannula member, the bone plate being a rigid body, typicallycomposed of metal, ceramic or hard polymer material, shaped tosufficiently conform for secure attachment to the surface of the bone tobe repaired or to provide a framing or base structure to properly alignthe bone or bone segments during healing, the bone plate having multiplescrew-receiving apertures through which bone screws are inserted tofixedly secure the bone plate to the underlying bone or bone segments.An elongated, tubular locking cannula is provided, the locking cannulaand bone plate being structured such that the cannula is temporarilymountable to the bone plate utilizing a threaded connection.

The screw receiving apertures are configured to comprise a proximal orexterior bore and a distal or interior bore, the distal bore beingsmaller in diameter than the proximal bore. The proximal bore isinternally threaded to receive an externally threaded end of the lockingcannula in order to temporarily secure the locking cannula to the boneplate. The distal bore of the screw receiving apertures may or may notbe internally threaded. The bone screws comprise a threaded shaftadapted to be driven into the bone and a screw head to preclude passageof the bone screw completely through the screw receiving aperture. Themaximum diameter of the bone screw is smaller than the internal diameterof the bore of the locking cannula. A pilot hole in the bone is createdby inserting an elongated, tubular drill guide into the locking cannula,then inserting a twist drill or drill bit into the drill guide andthrough the screw receiving aperture. The twist drill and drill guideare then removed from the locking cannula and the bone screw is passedthrough the locking cannula and into the screw receiving aperture, thendriven into the bone without requiring removal of the locking cannulafrom the bone plate.

In order to affix the bone plate to underlying bone or bone segments,the bone plate is positioned at its desired location and the lockingcannula is mounted to the bone plate. An elongated drill guide is theninserted into the locking cannula and a twist drill or drill bit isinserted into and through the drill guide and the corresponding screwreceiving aperture to create a screw-receiving pilot hole in the bone,the affixed locking cannula insuring that the pilot hole is properlyaligned relative to the screw receiving aperture and the bone plate. Thedrill and drill guide are removed and a bone screw is passed downthrough the locking cannula and inserted into the screw receivingaperture. An elongated drive tool is inserted into the locking cannulaand the bone screw is rotationally driven into the bore to secure thebone plate to the bone. These steps are repeated in successive screwreceiving apertures until the bone plate is securely fastened onto thebone.

In addition to an embodiment wherein a single locking cannula is usedwith each successive screw receiving apertures, in other embodiments allscrew-receiving apertures may each be provided with a dedicated lockingcannula, while in other embodiments the locking cannulas may bemountable only on selected apertures. The latter embodiment may benecessary when access space is limited. For the latter circumstance,once the bone screws have been properly affixed to the bone in theselected apertures such that the bone plate is secured in properposition on the bone, the locking cannulas are removed. Thescrew-receiving bores corresponding to the remaining apertures may becreated without the use of the locking cannulas. In still anotherembodiment, selected apertures may be structured to receive the lockingcannula, while other apertures on the bone plate may be standardthreaded or non-threaded apertures not adapted to receive the lockingcannula.

In alternative terms, the invention in various aspects is a bone platelocking cannula assembly comprising a bone plate comprising screwreceiving apertures, each said screw receiving aperture comprising aninternally threaded proximal bore having a proximal bore internaldiameter and a coaxially aligned distal bore having a distal boreinternal diameter, said proximal bore internal diameter being greaterthan said distal bore internal diameter; a locking cannula detachablymounted to one of said screw receiving apertures, said locking cannulahaving a proximal end, a tubular shaft, a longitudinal bore having alongitudinal bore internal diameter, and a distal end having externalthreading, said distal end sized and configured to be received by andmate with said internally threaded proximal bores of said screwreceiving apertures; and bone screws each comprising an externallythreaded shaft and a screw head, said bone screws being sized so as topass through said locking cannula longitudinal bore, wherein saidexternally threaded shaft is sized to pass through said distal bores ofsaid screw receiving apertures and said screw head is sized to beprecluded from passing through said distal bores of said screw receivingapertures. Furthermore, the invention is such an assembly wherein saiddistal bores are non-threaded; wherein said distal bores are internallythreaded; each of said screw receiving apertures further comprising atransition shoulder between said proximal bore and said distal bore, andwherein said distal end of said locking cannula contacts said transitionshoulder when said locking cannula is detachably mounted to said screwreceiving apertures; each of said screw receiving apertures furthercomprising a transition shoulder between said proximal bore and saiddistal bore, and wherein said screw heads are received within saiddistal bores and are precluded from passing through said distal bores bysaid transition shoulder; wherein said externally threaded distal end ofsaid locking cannula defines an abutment shoulder, and wherein saidabutment shoulder of said locking cannula contacts said bone plate whensaid locking cannula is detachably mounted to said screw receivingapertures; wherein said bone plate further comprises conventional screwreceiving apertures not adapted to receive said locking cannula; whereinsaid screw heads are externally threaded so as to be received by saidinternally threaded distal bores; further comprising a drill guide, saiddrill guide comprising an elongated tubular shaft and a drill guidelongitudinal bore, said tubular shaft having an external diametersmaller than said internal diameter of said locking cannula longitudinalbore such that said tubular shaft is removably received within saidlocking cannula longitudinal bore; said drill guide longitudinal borehaving an internal diameter smaller than said distal bore internaldiameter of said screw receiving apertures; further comprising a drillreceived within said drill guide longitudinal bore, said drill having anexternal diameter smaller than said internal diameter of said drillguide longitudinal bore; and/or further comprising additional lockingcannulas.

In alternative terms, the invention in various aspects is a bone platelocking cannula and drill guide assembly comprising a bone platecomprising screw receiving apertures, each said screw receiving aperturehaving an internally threaded proximal bore with approximal boreinternal diameter and a distal bore with a distal bore internaldiameter, said proximal bore and said distal bore being coaxial, saidproximal bore internal diameter being greater than said distal boreinternal diameter whereby a transition shoulder is disposed between saidproximal bore and said distal bore; at least one elongated lockingcannula detachably mounted to said screw receiving apertures, said atleast one locking cannula having a proximal end, a tubular shaft, alongitudinal bore having an internal diameter, and a distal end havingexternal threading, said externally threaded distal end sized andconfigured to threadingly mate with said internally threaded proximalbores of said screw receiving apertures to removably mount said at leastone locking cannula to said bone plate; at least one drill guide, saidat least one drill guide comprising an elongated tubular shaft and adrill guide longitudinal bore having an internal diameter, said tubularshaft having an external diameter smaller than said internal diameter ofsaid locking cannula longitudinal bore such that said tubular shaft isremovably received within said locking cannula longitudinal bore; andbone screws each comprising an externally threaded shaft and a screwhead having a maximum diameter, said internal diameter of said lockingcannula longitudinal bore being greater than said maximum diameter ofsaid screw head, such that said bone screw are passable through saidlocking cannula longitudinal bore, wherein said externally threadedshaft is sized to pass through said distal bore and said screw head issized to be precluded from passing through said distal bore by saidtransition shoulder. Furthermore, the assembly wherein said distal endof said at least one locking cannula contacts said transition shoulderwhen said at least one locking cannula is detachably mounted to saidscrew receiving apertures; said externally threaded distal end of saidat least one locking cannula defining an abutment shoulder, and whereinsaid abutment shoulder of said at least one locking cannula contactssaid bone plate when said at least one locking cannula is detachablymounted to said screw receiving apertures; wherein said bone platefurther comprises conventional screw receiving apertures not adapted toreceive said drill guides.

Alternatively, in other aspects, the invention is a method of affixing abone plate to bone comprising the steps of (a) providing a bone platelocking cannula and drill guide assembly comprising a bone platecomprising screw receiving apertures, each said screw receiving aperturehaving an internally threaded proximal bore with approximal boreinternal diameter and a distal bore with a distal bore internaldiameter, said proximal bore and said distal bore being coaxial, saidproximal bore internal diameter being greater than said distal boreinternal diameter whereby a transition shoulder is disposed between saidproximal bore and said distal bore; at least one elongated lockingcannula detachably mounted to said screw receiving apertures, said atleast one locking cannula having a proximal end, a tubular shaft, alongitudinal bore having an internal diameter, and a distal end havingexternal threading, said externally threaded distal end sized andconfigured to threadingly mate with said internally threaded proximalbores of said screw receiving apertures to removably mount said at leastone locking cannula to said bone plate; at least one drill guide, saidat least one drill guide comprising an elongated tubular shaft and adrill guide longitudinal bore having an internal diameter, said tubularshaft having an external diameter smaller than said internal diameter ofsaid locking cannula longitudinal bore such that said tubular shaft isremovably received within said locking cannula longitudinal bore; andbone screws each comprising an externally threaded shaft and a screwhead having a maximum diameter, said internal diameter of said lockingcannula longitudinal bore being greater than said maximum diameter ofsaid screw head, such that said bone screw are passable through saidlocking cannula longitudinal bore, wherein said externally threadedshaft is sized to pass through said distal bore and said screw head issized to be precluded from passing through said distal bore by saidtransition shoulder; (b) positioning said bone plate on a bone; (c)mounting said at least one locking cannula to one of said screwreceiving apertures; (d) inserting said drill guide into said lockingcannula; (e) providing a drill and inserting said drill into said drillguide and drilling a pilot hole into said bone through said one of saidscrew receiving apertures; (f) removing said drill and said drill guidefrom said locking cannula; (g) inserting a bone screw into said lockingcannula and driving said bone screw through said one of said screwreceiving apertures into said bone; (h) removing said locking cannulafrom said one of said screw receiving apertures; (i) mounting said atleast one locking cannula to another of said screw receiving apertures;and (j) repeating steps (d) through (h). Furthermore, the method whereinsaid step of providing a bone plate locking cannula and drill guideassembly comprises providing a bone plate having conventional screwreceiving apertures not adapted to matingly receive said at least onelocking cannula in addition to said screw receiving apertures adapted tomatingly receive said at least one locking cannula; and furthercomprising the step of driving said bone screws directly into bonethrough said conventional screw receiving apertures; and/or wherein saidstep of mounting said at least one locking cannula to one of said screwreceiving apertures is performed by first inserting said locking cannulathrough body tissue.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partial cross-sectional view of an embodiment of theinvention showing a portion of the bone plate, the screw receivingaperture, the locking cannula mounted to the bone plate, the drill guideinserted within the locking cannula and a drill guided by the drillguide and creating a pilot hole, the distal bore of the screw receivingaperture being non-threaded and comprising a shoulder to receive thescrew head.

FIG. 2 is a partial cross-sectional view of the embodiment of FIG. 1showing the locking cannula mounted to the bone plate, the drill anddrill guide having been removed from the locking cannula.

FIG. 3 is a partial cross-sectional view of the embodiment of FIG. 1showing the bone screw fully inserted into the screw receiving apertureprior to removal of the locking cannula from the bone plate.

FIG. 4 is a partial cross-sectional view of the embodiment of FIG. 1showing the bone screw fully inserted into the screw receiving apertureafter removal of the locking cannula from the bone plate.

FIG. 5 is a partial cross-sectional view of another embodiment of theinvention showing a portion of the bone plate, the screw receivingaperture, the locking cannula and the bone screw inserted into the bone,the distal bore of the screw receiving aperture being internallythreaded and receiving the externally threaded portion of the screwhead.

FIG. 6 is a partial cross-sectional view of another embodiment of theinvention showing a portion of the bone plate, the screw receivingaperture, the locking cannula and the bone screw inserted into the bone,the distal bore of the screw receiving aperture being internallythreaded to receive the externally threaded portion of the bone screwshaft, the diameter of the distal bore being significantly less than thediameter of the proximal bore such that a shoulder is defined toreceiver the screw head.

FIG. 7 is a plan view of the proximal side of a representativeembodiment of a bone plate.

FIG. 8 is a side view of the bone plate embodiment of FIG. 7.

FIG. 9 is a view of a representative embodiment of a locking cannula.

FIG. 10 is a view of a representative embodiment of a drill guide.

DETAILED DESCRIPTION OF THE INVENTION

With reference to the embodiments shown in the representative drawings,the number of which is not meant to be limiting in terms of the possibleembodiments or the scope and definition of the invention, the inventioncan be considered to comprise in general an assembly comprising a boneplate 10 and a locking cannula 20, as well as its method of use, thebone plate 10 being a rigid member, typically metal, ceramic or hadpolymer, shaped to conform to the surface of a bone or bone segments 99to be repaired or alternatively to provide a framework or base for rigidattachment of bone or bone segments 99, the bone plate 10 havingmultiple screw-receiving apertures 11 through which bone screws 30 areinserted to secure the bone plate 10 to the underlying bone or bonesegments 99. The bone plate 10 may be configured and structured tosecure a single bone or bone segments 99, or may be configured andstructures to connect bones or bone segments 99 to a distractor deviceor other instrumentation. Elongated, tubular locking cannulas 20 areprovided as part of the assembly, the locking cannulas 20 and boneplates 10 being structured such that the locking cannulas 20 aretemporarily mountable to the bone plate 10 utilizing a threadedconnection. The assembly may further comprise a tubular drill guide 40,the drill guide 40 being sized to so as to coaxially disposed within thelocking cannula 20. The drill guide 40 properly orients the drillrelative to the screw receiving aperture 11 during creation of a pilothole 98 to later receive the bone screw 30. The internal diameter 25 ofthe locking cannula 20 is greater than the maximum diameter 35 of thebone screw 30, such that upon removal of the drill guide 40 from thelocking cannula 20, the bone screw 30 may be delivered through thelocking cannula 20 and inserted into the bone 99 without requiringremoval of the locking cannula from the bone plate 10.

As used herein, terms such as proximal shall refer to the side ordirection away from the bone or bone segments 99 to which the bone plate10 is being affixed, while terms such as distal shall refer to the sideor direction toward the bone or bone segments 99 to which the bone plate10 is being affixed. In terms of the surgeon implanting the bone plate10, proximal is toward or near to the surgeon and distal is away arefarther from the surgeon.

The hollow, longitudinally bored, tubular locking cannula 20 comprised atubular shaft 21 having a longitudinal bore 27, the locking cannula 20having a proximal end 26 and a distal end 22. The distal end 22 isprovided with external threading 23 adapted to mate with internalthreading 16 present in the proximal bore 13 of the bone plate 10. Thethreaded distal end 22 may be reduced in external diameter relative tothe tubular shaft 21 to define an abutment shoulder 24 that functions tostop advancement of the locking cannula 20 into the bone plate 10, asshown in FIGS. 1 and 5, or the connection between the bone plate 10 andthe locking cannula 20 may be structured such that the distal end 22bottoms out on the transition shoulder 18 between the proximal bore 13and the distal bore 12 of the base plate aperture 11 without theabutment shoulder 24 contacting the base plate 10, as shown in FIG. 6.With this structure the locking cannula 20 may be temporarily yetrigidly mounted onto bone plate 10 and subsequently removed from thebone plate 10 by rotating the locking cannula 20 relative to the boneplate 10, preferably utilizing a handled trocar or other member ormechanism to provide for manual rotation of the locking cannula 20.

The screw receiving apertures 11 are structured to comprise a proximalor exterior bore 13 and a coaxial distal or interior bore 12, the distalbore 12 having an internal diameter 14 lesser than the internal diameter15 of the proximal bore 13 such that a transition shoulder 18 is formedbetween the proximal bore 13 and the distal bore 12. The proximal bore13 comprises internal threading 16 to receive and mate with externalthreading 23 disposed on the distal end 22 of the locking cannula 20.The distal bore 20 may or may not be internally threaded. The embodimentof FIG. 1 shows a non-threaded distal bore 20 while the embodiments ofFIGS. 5 and 6 show threaded distal bores 20. In the embodiment of FIG.5, the distal bore 20 is tapered in the distal direction, with theinternal diameter 14 as used herein being defined as the maximumdiameter of the distal bore 20. The provision of a larger proximal bore13 and a smaller distal bore 12 is desirable as with this structure thescrew head 32 is received in a recessed manner and does notsignificantly protrude above the exterior or proximal surface of thebone plate 10 once implanted. Most preferably the depth of the proximalbore 13 is equal to or greater than the depth of the screw head 32, suchthat no portion of the screw head 32 extends above the exterior surfaceof the bone plate 10 once the bone screw 30 is fully inserted.

The bone screws 30 each comprise a threaded shaft 31 with externalthreading 34, adapted to extend through the bone plate 10 to be receivedby the bone 99, and a larger screw head 32, preferably circular todefine a maximum diameter 35 adapted to preclude passage of the bonescrew 30 completely through the bone plate 10. The screw head 32 isstructured in known manner, e.g., slotted or provided with anon-circular recess, to receive the end of a drive tool, e.g., ascrewdriver. The maximum diameter 35 of the screw head 32, and anyportion of the bone screw 30, is smaller than the internal diameter 25of the locking cannula bore 27, such that the bone screw 30 may beinserted through the proximal end 26 down through tubular shaft 21 andpast the distal end 22 of the locking cannula 20 such that the threadedshaft 31 extends into and through the screw receiving aperture 11,whereupon it may be driven into the bone 99. In this manner the threadedshaft 31 extends through the screw receiving aperture 11 into the bone99, while the transition shoulder 18 between the proximal bore 13 andthe distal bore 12 defines a stop against further advancement of thescrew head 32, the screw head maximum diameter 35 being greater than thedistal bore diameter 14. The screw head 32 may be provided with nothreading, as shown in FIGS. 1 and 6, or may be provided with externalthreading 33, as shown in FIG. 5.

All of the apertures 11 of the bone plate 10 may be structured totemporarily receive the locking cannulas 20. Alternatively, asillustrated in FIGS. 7 and 8, the bone plate 10 may be provided withsome apertures 11 capable of receiving the drill guides and otherconventional screw receiving apertures 19, either threaded ornon-threaded, through which bone screws 30 may be driven, suchconventional apertures 19 lacking the proximal bore/distal borestructure required for mounting the locking cannula 20 to the bone plate10.

In certain embodiments the assembly further comprises an elongated,hollow drill guide 40 having an elongated tubular shaft 41, a distal end42, a proximal end 46, a longitudinal bore 47 and a handle 45. Thetubular shaft 41 has an external diameter 44 and the longitudinal bore47 has an internal diameter 44. A representative drill guide 40 is shownin FIGS. 1 and 10. The drill guide external diameter 44 is smaller thanthe internal diameter 25 of the locking cannula longitudinal bore 27,such that the drill guide tubular shaft 41 is coaxially insertable intothe locking cannula longitudinal bore 27, as shown in FIG. 1. The drillguide internal diameter 43 is smaller than the distal bore diameter 14of the bone plate 10. The assembly may further comprise a drill or drillbit 50, such as a manual twist drill for example, wherein the externaldiameter 51 of the drill 50 is smaller than the drill guide internaldiameter 43 and smaller than the distal bore diameter 14 of the boneplate 10, as seen in FIG. 1. The drill 50 is utilized to create a pilotbore or hole 98 to receive a bone screw threaded shaft 31 in normalmanner.

In one embodiment of the method, such as for a transbuccal implantationfor example, the bone plate 10 is positioned against the bone 99 at thedesired attachment location. The distal end 22 of the tubular shaft 21of the locking cannula 20 is inserted through a small incision orpuncture in the cheek tissue in known manner, typically with a trocarinserted into the longitudinal bore 27 to occlude the longitudinal bore27 during insertion. The locking cannula 20 is aligned with the proximalbore 13 of one of the screw receiving apertures 11 and axially rotatedsuch that the locking cannula external threading 23 mates with theproximal bore internal threading 16, thereby properly coaxially aligningand orienting the axis of the locking cannula 20 to the axis of theproximal bore 13 and the shared axis of the distal bore 12. The trocaris removed and the drill guide 40 is inserted into the locking cannula20 such that the axis of the drill guide longitudinal bore 47 iscoaxially aligned with the axis of the locking cannula longitudinal bore27. The drill 50 is then inserted into the drill guide 40 and acentered, coaxially aligned pilot hole 98 is created in the bone 99, asshown in FIG. 1.

The drill 50 and the drill guide 40 are then removed from the lockingcannula 20, as shown in FIG. 2. Because the internal diameter 25 of thelocking cannula internal bore 27 is greater than the external diameter44 of the bone screw 30, the bone screw is inserted into the proximalend 26 of the locking cannula 20 and guided or funneled to the screwreceiving aperture 11. Utilizing a drive tool, not shown, the externallythreaded shaft 31 of the bone screw 30 is maneuvered through theaperture 11 and into the pilot hole 98, then rotated in known mannersuch that the bone screw 30 advances into the bone 99. As the bone screw30 is advanced the distal side of the screw head 32 abuts the abutmentshoulder 24 between the wider proximal bore 13 and the narrower distalbore 12 of the screw receiving aperture 11, such that the plate 10 isaffixed securely on the bone 99, as shown in FIG. 3. The presence of thelocking cannula 20 further insures that the bone screw 30 is properlyoriented into the bone 99 relative to the bone palte aperture 11. Withthe bone screw 30 fully inserted, the locking cannula 20 is now rotatedand removed from the bone plate 10. For implantation of subsequent bonescrews 30 the process is then repeated from the step of inserting thelocking cannula 20 through the cheek forward. The description of atransbuccal implantation is not meant to be limiting, as the assemblyand its methodology may be utilized at other locations.

In an alternate method embodiment in circumstances where the attachmentzone for the bone plate 10 is adequately exposed, plural lockingcannulas 20 are mounted to some or all of the screw receiving apertures10 on the bone plate 10 and the bone plate 10 is positioned at theproper location on the bone or bone segments 99. The bone screws 30 arethen inserted into the bone 99 as set forth above and with the boneplate 30 properly secured to the bone 99, the locking cannulas 20 areremoved from the bone plate 10. In still another alternate methodembodiment, wherein some of the screw receiving apertures 11 are coveredby body tissue and other apertures 19 are externally exposed, thelocking cannulas 20 may be utilized for the covered apertures 11 in themanner set forth above and bone screws 30 may be inserted in directmanner into the conventional screw receiving apertures 19, theconventional screw receiving apertures 19 not having any internalthreading.

The embodiments discussed and illustrated are not meant to be limiting,and it is understood and contemplated that equivalents and substitutionsfor some elements set forth above may be obvious to those of skill inthe art, and therefore the true scope and definition of the invention isto be as set forth in the following claims.

We claim:
 1. A method of affixing a bone plate to bone comprising thesteps of: (a) providing a bone plate locking cannula and drill guideassembly comprising: a bone plate comprising screw receiving apertures,each said screw receiving aperture having an internally threadedproximal bore with a proximal bore internal diameter and a distal borehaving a distal bore internal diameter, said proximal bore and saiddistal bore being coaxial, said proximal bore internal diameter beinggreater than said distal bore internal diameter whereby a transitionshoulder is disposed between said proximal bore and said distal bore; atleast one elongated locking cannula detachably mounted to said screwreceiving apertures, said at least one locking cannula having a proximalend, a tubular shaft, a longitudinal bore having an internal diameter,and a distal end having external threading, said externally threadeddistal end sized and configured to threadingly mate with said internallythreaded proximal bores of said screw receiving apertures to removablymount said at least one locking cannula to said bone plate; at least onedrill guide, said at least one drill guide comprising an elongatedtubular shaft and a drill guide longitudinal bore having an internaldiameter, said tubular shaft having an external diameter smaller thansaid internal diameter of said locking cannula longitudinal bore suchthat said tubular shaft is removably received within said lockingcannula longitudinal bore; and bone screws each comprising an externallythreaded shaft and a screw head having a maximum diameter, said internaldiameter of said locking cannula longitudinal bore being greater thansaid maximum diameter of said screw head, such that said screw heads ofsaid bone screws are sized so as to pass completely through said lockingcannula longitudinal bore and said locking cannula distal end, whereinsaid externally threaded shaft is sized to pass through said distal boreof said screw receiving aperture and said screw head is sized to beprecluded from passing through said distal bore by said transitionshoulder of said screw receiving aperture; (b) positioning said boneplate on a bone; (c) mounting said at least one locking cannula to oneof said screw receiving apertures; (d) inserting said drill guide intosaid locking cannula; (e) providing a drill and inserting said drillinto said drill guide and drilling a pilot hole into said bone throughsaid one of said screw receiving apertures; (f) removing said drill andsaid drill guide from said at least one locking cannula; (g) inserting abone screw into said at least one locking cannula and driving said bonescrew into said bone through said one of said screw receiving aperturesand through said pilot hole; (h) removing said at least one lockingcannula from said one of said screw receiving apertures; (i) mountingsaid at least one locking cannula to another of said screw receivingapertures; and (j) repeating steps (d) through (h).
 2. The method ofclaim 1, wherein said step of providing a bone plate locking cannula anddrill guide assembly comprises providing a bone plate havingconventional screw receiving apertures not adapted to matingly receivesaid at least one locking cannula in addition to said screw receivingapertures adapted to matingly receive said at least one locking cannula;and further comprising the step of driving said bone screws directlyinto bone through said conventional screw receiving apertures.
 3. Themethod of claim 2, wherein said step of mounting said at least onelocking cannula to one of said screw receiving apertures is performed byfirst inserting said at least one locking cannula through body tissue.4. The method of claim 1, wherein said step of mounting said at leastone locking cannula to one of said screw receiving apertures isperformed by first inserting said at least one locking cannula throughbody tissue.
 5. A method of affixing a bone plate to bone comprising thesteps of: (a) providing a bone plate locking cannula and drill guideassembly comprising: a bone plate comprising screw receiving apertures,each said screw receiving aperture comprising an internally threadedproximal bore having a proximal bore internal diameter and a coaxiallyaligned distal bore having a distal bore internal diameter, saidproximal bore internal diameter being greater than said distal boreinternal diameter; a locking cannula detachably mounted to one of saidscrew receiving apertures, said locking cannula having a proximal end, atubular shaft, a longitudinal bore having a longitudinal bore internaldiameter, and a distal end having external threading, said distal endsized and configured to be received by and mate with said internallythreaded proximal bores of said screw receiving apertures; a drillguide, said drill guide comprising an elongated tubular shaft and adrill guide longitudinal bore, said tubular shaft having an externaldiameter smaller than said internal diameter of said locking cannulalongitudinal bore such that said tubular shaft is removably receivedwithin said locking cannula longitudinal bore; and bone screws eachcomprising an externally threaded shaft and a screw head, said screwheads of said bone screws being sized so as to pass completely throughsaid locking cannula longitudinal bore and said locking cannula distalend, wherein said externally threaded shaft is sized to pass throughsaid distal bores of said screw receiving apertures and said screw headis sized to be precluded from passing through said distal bores of saidscrew receiving apertures; (b) positioning said bone plate on a bone;(c) mounting said locking cannula to one of said screw receivingapertures; (d) inserting said drill guide into said locking cannula; (e)providing a drill and inserting said drill into said drill guide anddrilling a pilot hole into said bone through said one of said screwreceiving apertures; (f) removing said drill and said drill guide fromsaid locking cannula; (g) inserting a bone screw into said lockingcannula and driving said bone screw into said bone through said one ofsaid screw receiving apertures and through said pilot hole; (h) removingsaid locking cannula from said one of said screw receiving apertures;(i) mounting said locking cannula to another of said screw receivingapertures; and (j) repeating steps (d) through (h).
 6. The method ofclaim 5, wherein said step of providing a bone plate locking cannula anddrill guide assembly comprises providing a bone plate havingconventional screw receiving apertures not adapted to matingly receivesaid locking cannula in addition to said screw receiving aperturesadapted to matingly receive said locking cannula; and further comprisingthe step of driving said bone screws directly into bone through saidconventional screw receiving apertures.
 7. The method of claim 6,wherein said step of mounting said locking cannula to one of said screwreceiving apertures is performed by first inserting said locking cannulathrough body tissue.
 8. The method of claim 5, wherein said step ofmounting said locking cannula to one of said screw receiving aperturesis performed by first inserting said locking cannula through bodytissue.
 9. A method of affixing a bone plate to bone comprising thesteps of: (a) providing a bone plate locking cannula and drill guideassembly comprising: a bone plate comprising screw receiving apertures,each said screw receiving aperture comprising an internally threadedproximal bore having a proximal bore internal diameter and a coaxiallyaligned distal bore having a distal bore internal diameter, saidproximal bore internal diameter being greater than said distal boreinternal diameter; a plurality of locking cannulas detachably eachmounted to a plurality of said screw receiving apertures, each of saidlocking cannulas having a proximal end, a tubular shaft, a longitudinalbore having a longitudinal bore internal diameter, and a distal endhaving external threading, said distal end sized and configured to bereceived by and mate with said internally threaded proximal bores ofsaid screw receiving apertures; one or more drill guides, each saiddrill guide comprising an elongated tubular shaft and a drill guidelongitudinal bore, said tubular shaft having an external diametersmaller than said internal diameter of each said locking cannulalongitudinal bore such that said tubular shaft may be removably receivedwithin each of said locking cannula longitudinal bores; and bone screwseach comprising an externally threaded shaft and a screw head, saidscrew heads of said bone screws being sized so as to pass completelythrough said locking cannula longitudinal bores and said locking cannuladistal ends, wherein said externally threaded shaft is sized to passthrough said distal bores of said screw receiving apertures and saidscrew head is sized to be precluded from passing through said distalbores of said screw receiving apertures; (b) positioning said bone plateon a bone; (c) mounting said locking cannulas to said screw receivingapertures; (d) inserting said one or more drill guides into one or moreof said locking cannulas; (e) providing a drill and inserting said drillinto each said drill guide and drilling a pilot hole into said bonethrough said one of said screw receiving apertures; (f) removing saiddrill and said drill guides from said locking cannulas; (g) inserting abone screw into each of said locking cannulas and driving said bonescrew into said bone through said one of said screw receiving aperturesand through said pilot hole; and (h) removing said locking cannulas fromsaid screw receiving apertures.
 10. The method of claim 9, wherein saidstep of providing a bone plate locking cannula and drill guide assemblycomprises providing a bone plate having conventional screw receivingapertures not adapted to matingly receive said locking cannulas inaddition to said screw receiving apertures adapted to matingly receivesaid locking cannulas; and further comprising the step of driving saidbone screws directly into bone through said conventional screw receivingapertures.
 11. The method of claim 10, wherein said step of mountingsaid locking cannulaa to said screw receiving apertures is performed byfirst inserting said locking cannula through body tissue.
 12. The methodof claim 9, wherein said step of mounting said locking cannulas to saidscrew receiving apertures is performed by first inserting said lockingcannulas through body tissue.